Tracking freshwater snail diversity: a historical and environmental study in sub-tropical South Africa

Abstract Freshwater snails are integral to aquatic ecosystems, contributing to nutrient cycling and serving as bioindicators of environmental health. However, this group faces growing threats from human activities, habitat degradation, and invasive species. This study investigated the diversity, distribution, and abundance of freshwater snails in a sub-tropical South African region, comparing current populations with historical data from the 1960s–1980s. The ecological impacts of invasive species on native snails and ecosystem functions were also assessed. Field surveys at multiple sites, employing qualitative and quantitative collection methods, measured snail populations alongside water quality and habitat characteristics. Multivariate analyses, including canonical correspondence analysis (CCA), explored the relationships between environmental variables and snail community composition. Nine freshwater snail taxa were identified, with the invasive Tarebia granifera —absent from historical records—dominating. CCA results showed distinct differences in community composition between sites with and without T. granifera . The presence of this invasive species corresponded with reduced diversity and abundance of native snails, particularly in fast-flowing habitats with limited aquatic vegetation. This research highlights the need for monitoring native and invasive species, highlighting conservation priorities to protect native snails and mitigate the ecological and human health impacts of invasive species.